1. Field of the Invention
This invention relates to a laminar damper and method for controlling the flow of air or any other gas or fluid at low differential pressures.
2. Discussion of the Background
The state of the art dampers fall into three general categories, these being: sliding dampers (FIGS. 6A, 6B), opposed blade dampers (FIGS. 7A, 7B) and louvered dampers (FIG. 8). The sliding blade dampers function by using two plates with perforations that are slid across one another to control the flow through the holes. These dampers at the fully open position block at least 50% of the opening and create accelerated flow through sharp edged openings, which thus create turbulence in the downstream flow. This results in the flow velocity profile shown in FIG. 6B. The opposed blade dampers consist of plates arranged on spindles so that the plates can rotate, each plate rotating in the opposite direction to that of its neighbor. This type of damper does not restrict the flow through the opening in the fully open position and when the damper is closed the edges of the plates touch. In the partially open condition the blades force the flow into convergent and divergent streams as shown in FIG. 7A, thus creating a nonuniform velocity profile as shown in FIG. 7B and turbulence across the controlled flow. The louvered dampers are similar to the opposed blade dampers except that the blades rotate in the same direction as shown in FIG. 8. In partially open conditions, the flow is diverted by the blades and exits from the damper at a varying angle depending upon the control setting. Low flow rates create turbulence due to the separation of the airflow around the blade.